The aim of this research proposal is to characterize monocyte/macrophage immune surveillance by defining the homeostatic trafficking signals used by these cells. Projects will include the isolation of hematopoietic progenitors and differentiation of these cells into myeloid cells to discern the phenotype and functional properties of various tissue specific macrophage populations. Other projects will include cloning and characterization of monocyte/macrophage specific genes involved in monocyte to macrophage/and or dendritic cell differentiation and cell trafficking. Projects: 1. In vitro differentiation of progenitors into monocytes -> macrophages/dendritic cells. 2. Ex vivo transfer of differentiated cells into recipient mice. 3. Characterization of monocyte/macrophage/dendritic cell specific genes or proteins. 4. Macrophage/dendritic cell apoptosis.